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<br />INTERMOUNTAIN WEST CLIMATE SUMMARY, JUNE 2006
<br />
<br />Advances in Soil Moisture Science: New in situ soil
<br />moisture measurements from NRCS
<br />
<br />Figure 14a: (Left) Using new sensors, soil moisture chart for
<br />the state of Utah for 2005 and 2006 is generated by compiling
<br />monthly averages of soil moisture from various watershed basins
<br />around the state.
<br />Figure 14b: (Right) Soil moisture chart for Uintah Basin in 2005
<br />and 2006 plotted using monthly averages of soil moisture col-
<br />lected from1 0-16 different sites.
<br />
<br />have a broader range of scientific applications, including drought
<br />monitoring and climate change.
<br />As of 2005, the agency has installed over 1000 of these sen-
<br />sors, according to Dr. Thomas Pagano, water supply forecaster
<br />of the NRCS National Water and Climate Center (NWCC) in
<br />Portland, Oregon. Many of these sensors are in the mountains of
<br />the Western US, coupled with the SNOTEL net\vork, \vhile many
<br />are also part of the Soil Climate Analysis Network (SCAN) in
<br />regions including Ha\vaii, Puerto Rico, the Eastern US, and even
<br />Antarctica. In the Western US, Utah has developed excellent
<br />geographic coverage of sensors and has acquired a long enough
<br />period of record to generate real time graphical products for us-
<br />ers. These include soil moisture time series charts (Figures 14a
<br />and 14b) and a state Soil Moisture Update Report, available on
<br />the web (see URLs below). These complement the basic suite of
<br />tabular products available at the NWCC \vebpage.
<br />The primary objective is to measure soil moisture and temper-
<br />ature, although other data such as capacitance and conductance
<br />are also available from the sensors. The sensors are typically
<br />
<br />On the Web
<br />- NRCS: Climate Information, including soil moisture charts and the Utah Soil Moisture Update Report:
<br />http://www. ut. n rcs. usda. gov /snow /cl i mate/
<br />- NRCS: Field Office Guide to Climatic Data: http://www.wcc.nrcs.usda.gov/climate/foguide.html
<br />
<br />By Christina Alvord, Western Water Assessment
<br />
<br />There is a new technology in the world of soil moisture
<br />monitoring and research, the Stevens Hydroprobe sensor, \vhich
<br />measures soil moisture and soil temperatures. This technology
<br />is being used by the Natural Resources Conservation Service
<br />(NRCS) to better measure impacts of dry or \vet soils on sea-
<br />sonal run-off. The study and management of soils is one compo-
<br />nent of the NRCS mission, which includes the conservation of
<br />soil, \vater, air, plants, and animals -- the "SWAPA" resources.
<br />Climate and hydrology serve as a common thread, linking all of
<br />the various resources, and detailed quality data are key to better
<br />understanding. In particular, data from these ne\v soil moisture
<br />and temperature sensors are useful for improving seasonal water
<br />supply outlooks and on-the-ground irrigation decisions but also
<br />
<br />Statewide Soil Moisture
<br />1-. 2006 --20051
<br />
<br />Uintah Basin Soil Mois.ture
<br />1-. 2006 __20051
<br />
<br />100%
<br />
<br />
<br />100%
<br />
<br />80%
<br />
<br />80%
<br />
<br />
<br />60%
<br />
<br />~
<br />0 60%
<br />:;:;
<br />E
<br />:::J
<br />10
<br />(j) 40%
<br />'#
<br /> 20%
<br />
<br />40%
<br />
<br />20%
<br />
<br />0%
<br />
<br />0%
<br />
<br />O~O~0(J,,:>'f)"<<~~~ ~q~f(J.\';:''' ,:>~,>04JZqJ
<br />Date
<br />
<br />O~O~0(J,::>'f)<:-<<~~~ ~q~'f)\';:'<:- ,:>~,>\eq
<br />Date
<br />
<br />I~ N RCS~
<br />
<br />placed at 2, 8, and 20 inch depths in the soil to measure these
<br />parameters at 10-16 sites within each large basin. Sensor read-
<br />ings are weighted in proportion to corresponding depths (Figure
<br />14c). The 2 inch depth sensor represents the first 6 inches of soil
<br />starting at the soil surface, the 8 inch sensor represents the next
<br />consecutive 9 inches of soil and the 20 inch sensor measures the
<br />following consecutive 12 inches with a total measurement of 26
<br />inches of soil. Each month, NRCS generates graphs of the data
<br />(Figures 14a and 14b) which display the average percentage of
<br />ground saturation for each watershed basin and region being
<br />measured.
<br />Already these data are being used to improve the water sup-
<br />ply outlooks; Randall Julander, Snow Survey Supervisor for the
<br />Utah NRCS, says that based on preliminary results on a small
<br />Utah \vatershed, Centerville Creek, the data recorded using these
<br />sensors saw "substantial improvement in predictive capabil-
<br />ity over using sno\v data alone." By kno\ving the soil moisture
<br />deficit, one can better estimate the anticipated seasonal runoff
<br />efficiency; are the soils full and will the snowmelt directly feed
<br />the streams? Or \vill the soils capture most of the moisture?
<br />"These data should also give us a better handle on significant
<br />sublimation events" indicated Dr. Pagano. "Before, if the snow
<br />\vas disappearing, it \vould be hard to know if it was going into
<br />the soils or disappearing into the sky. Now we can track that as it
<br />happens and adjust accordingly."
<br />Julander's experience has been that these sensors are a low
<br />maintenance, reliable technology that provides a consistent, uni-
<br />fied method of measuring soil moisture. Based on initial
<br />
<br />Placement of Stevens Hydraprobe Sensors
<br />
<br />Soil Depth . Soil Increments
<br />~~~:;:~~c~:S) S~i~ ;~~:~~ ... ........ .:. ....... Measured (depth in inches)
<br />2" depth
<br />-e
<br />
<br />8" depth - e
<br />
<br />> 0-6"
<br />
<br />20"depth - e
<br />
<br />) 6-14"
<br />
<br />
<br />) 14-26'
<br />
<br />26" below soil surface
<br />
<br />Figure 14c: Descriptive graph of sensor placement within soil
<br />where 3 sensors are used at every site within each watershed
<br />basin.
<br />
<br />successes, NRCS plans to implement these sensors at all
<br />SNOTEL sites in Utah, Nevada, and the Sierras. At this pace, it
<br />should not be long until this investment matures into quantitative
<br />improvements in water supply forecasts and management prac-
<br />tices. In time, this data stream may also become an indispensable
<br />part of the national and global climate monitoring network.
<br />
<br />FocuS PAGE 11 8
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